1. Field of the Invention
The present invention relates to a monitor screen control apparatus which receives video and synchronizing signals from a host computer and automatically displays screen images in the middle of screen of a monitor regardless of computer-supported display modes, and a method for automatically controlling the centering of the monitor screen.
2. Description of the Related Art
A computer monitor is provided to display text and/or graphic information from a host computer on the screen thereof. Such a computer monitor allows the display of screen images in accordance with display modes, such as a variety of text and graphic modes, which are supported by the host computer. For example, the computer monitor receives text information from the computer and displays it on the screen thereof with a text mode. The computer monitor also receives graphic information from the computer and displays it on the screen thereof with a graphic mode.
A typical personal computer may have an associated monitor serving as a display apparatus, a keyboard and a printer, a light pen or plotter. The monitor associated with the computer is connected to a graphic card, for instance, a VGA card of the computer via a video cable. The computer provides video signals, e.g., R(red), G(green) and B(blue) video signals, vertical and horizontal synchronization signals V.sub.-- Sync and H.sub.-- Sync, and overall control information required to control the monitor, to the monitor through the video cable. Also, through the video cable, information indicative of the monitor-processed results from the monitor are provided to the computer. The monitor has a monitor circuit and a CRT (cathode ray tube). Thus, the monitor displays video signals R, G and B on the CRT in synchronism with the vertical and horizontal synchronization signals which are supplied from the VGA card of the computer in accordance with the computer-supported display modes. The monitor, however, has a problem in that the image is not displayed in the middle of the monitor screen or partially displaced on the monitor in accordance with the display modes. Since the partially displaced image is beyond the range of the display on the screen, an operator cannot view the displaced image using the monitor.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited technique for automatically controlling the centering of a monitor screen as in the present invention: U.S. Pat. No. 5,555,002 to Nguyen, entitled Method And Display Control System For Panning, U.S. Pat. No. 5,572,259 to Nohara, entitled Method Of Changing Personal Computer Monitor Output For Use By A General Purpose Video Display, U.S. Pat. No. 5,621,428 to King et al., entitled Automatic Alignment Of Video Window On A Multimedia Screen, U.S. Pat. No. 4,991,022 to Canfield et al., entitled Apparatus And A Method For Automatically Centering A Video Zoom And Pan Display, U.S. Pat. No. 5,592,194 to Nishikawa, entitled Display Controller, U.S. Pat. No.5,335,296 to Larkin et al., entitled Process For High Speed Rescaling Of Binary Images, U.S. Pat. No.5,457,473 to Arai et al., entitled Image Display Apparatus, U.S. Pat. No. 5,477,241 to Higgins et al., entitled Method Of Resetting A Computer Video Display Mode, U.S. Pat. No. 4,990,902 to Zenda, entitled Display Area Control System For Flat Panel Display Device, U.S. Pat. No.4,574,279 to Roberts, entitled Video Display System Having Multiple Selectable Screen Formats, and U.S. Pat. No. 4,754,270 to Murauchi, entitled Apparatus For Varying The Size And Shape Of An Image In A Raster Scanning Type Display.